1. Field of the Invention
The present invention relates to a method for preparing methacrolein through gas phase catalytic oxidation of isobutylene or a tertiary butanol with molecular oxygen.
2. Description of the Prior Art
Heretofore, there have been proposed a variety of catalysts used in the preparation of methacrolein through gas phase catalytic oxidation of isobutylene or a tertiary butanol with molecular oxygen For instance, Japanese Unexamined Patent Publication No. Sho 63-107745 discloses a catalyst which comprises a rare earth element. The patent also discloses that antimony is an essential component in order to obtain a catalyst having high selectivity to end products and that it is necessary to use, as a starting material for the catalyst, antimony trioxide having an average particle size of the order of 0.2 .mu.m or smaller which cannot be obtained through methods other than the metal vapor deposition method. Moreover, Japanese Unexamined Patent Publication No Sho 63-315147 also discloses a catalyst which comprises a rare earth element, but the catalyst is prepared according to a special method and the activity and selectivity thereof are not yet sufficient.
As has been discussed above, the conventional catalysts for preparing methacrolein are still insufficient in the quality thereof such as the activity, the selectivity to methacrolein, the stability and the duration of life thereof. Thus, there have been desired for the improvement of the quality of these catalysts.